No antibacterial activity by themselves because they only have half of the beta-lactam part, used in combination to act as a decoy and consume the penicillinase/beta-lactamase and keep the antibiotic or penicillin protected

Carbapenems BS Activity

● Advantages at three different sites allows broader spectrum and increased efficacy

→ Improved penetration of porins

→ Enhanced binding to PBP (transpeptidase)

→ Increased resistance to b-lactamases

Imipenem (Carbapenem) with Cilastatin (Primaxin)

● Inhibit renal dehydropeptidase

● Imipenem is inactivated by dehydropeptidase in renal tubules

Bacitracin Advantage

No cross resistance between Bacitracin and other antimicrobial agents

Sulfonamide / Trimethoprim Combination

● Combination is bactericidal

● Trimethoprim + sulfamethoxazole

● Sulfadiazine + pyrimethamine

● Sulfadoxine + Pyrimethamine (Fansidar)

Sulfonamides Ineffective Against

● Rickettsiae

● Anaerobes

● Pseudomonas

Aminoglycosides + B-lactam

● Extend coverage to gram+ pathogens

● Take advantage of the synergism between these two classes of drugs

● Enterococcal endocarditis

● Shorten duration of therapy for

→ Viridans streptococcal infections

→ Staphylococcal endocarditis

Tetracycline Absorption

● Food (except doxycycline and minocycline)

● Divalent cations (Ca2+, Mg2+, Fe2+) or Al3+

● Dairy products and antacids, which contain multivalent cations

● Alkaline pH

Methenamine CI w/Sulfonamides

Sulfonamides should not be given at the same time because they may form an insoluble compound with the formaldehyde released by methenamine (exacerbate crystalluria)